An electrician in theatre is someone who uses electricity to make the stage lights work properly and make the show look amazing. They know how to connect wires and make sure the lights are shining in the right direction.
It's like playing with a big, fancy puzzle where all the pieces are wires and bulbs. They plug things in, turn them on, and make sure they stay on during the show.
They also work with other people on the crew, like the stage manager, to make sure everything is ready to go before the show starts. They might have to climb up high to hang lights or crawl under the stage to fix something, but they always make sure everything is safe before they do it.
Basically, electricians in theatre make sure the lights are working so the show can go on!